1. Technical Field
This invention relates to electrolytic capacitors. More particularly it relates to compact electrolytic capacitors that have a plurality of electrically conductive anodes, an electrically conductive cathode, and an electrolyte between the anodes and cathode. The invention also concerns a method for making such capacitors. While the applicability of the present invention is broad and general, for the sake of an orderly presentation, and to facilitate the comprehension of the principles of the invention, the description focuses principally on the structural characteristics of and manufacturing methods for capacitors which are designed to be used in implantable biomedical electronic devices such as defibrillators.
2. Background Art
Defibrillator designed for implantation inside the human body require associated power supplies which must be provided with a high capacitance in order to be able to deliver on demand intense bursts of current for very short time intervals. The battery used in defibrillator cannot deliver a large burst of energy, so an intermediate storage medium such as an electrolytic capacitor is used to accumulate the energy over a period of about 10 seconds and deliver it to the heart in about 5 milliseconds. Electrolytic capacitors are well suited for performing this function in biomedical electronic devices. Given the environment within which such a device is used, however, it is essential that the volume of the device be kept to an absolute minimum. Thus, since the capacitor in such a device ordinarily occupies as much as about 30% of the total volume of the device, considerable effort has been expended on the problem of reducing the size of the capacitor. Nevertheless, attempts to minimize the volume of electrolytic capacitors have met with only limited degrees of success, for a number of reasons.